I noticed similar effect with very recent (4.17) kernels. In 4.16.8 there were changes in random.c due to a security flaw. The function that detects "having enough entropy" is now strictly blocking. In the early boot phase this is bad on any machine without enough entropy sources. The kernel has 3 such sources: character devices, block devices and interrupts. On newer machines you can also have hardware random engines like in intel cores gen3+ (ivy bridge). This effect does not appear on computers with such a hw-rng. If you have one without hw-rng, and with a SSD only (they are not used for entropy gathering) and you don't mode your mouse, you are likely seeing this. The bad thing is, this kernel patch is actually necessary to prevent the system starting with insufficient safe random numbers. I applied a patch that reverts commit 43838a23a05fbd13e47d750d3dfd77001536dd33 in the kernel. After this change the startup worked like expected, but this is not a solution as it re-invents CVE-2018-1108. An idea would be to add a hw-rng like https://www.crowdsupply.com/13-37/infinite-noise-trng, but i did not test that so far. Check your cpu for the rdrand flag (lscpu). An entropy deamon like rngd helps only if you have entropy sources that it can use.
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1779827 Title: failure to boot with linux-image-4.15.0-24-generic Status in Ubuntu: Confirmed Status in linux package in Ubuntu: Fix Released Status in The Bionic Beaver: Confirmed Status in linux source package in Bionic: Fix Released Bug description: This was the last OK then my 18.04 hangs after an update this morning. 07:00 AM CEST Last Ok in boot was Started gnome display manager. dispatcher service ...... tem changes.pp link was shut down Tried install lightdm from command line and the response was lastest already installed. Probably it is what is coming after the lastest OK which is to be the error. And here I have lots of guesses...... Any Ideas ? I need to do some work and I may not be waiting long. Search and browsed and now close to give up. Yeah it is a Lenovo. Guys: turn of auto update it is a machine killer. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1779827/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
